Engine Update

[BIGTWIN]

Hey Scotty, I agree, it's that old technology engine design that is what bothers me in the whole picture too. I worry about the unleaded gas as well since the lead protects the valves. I try to stick with the viscosity of oil the manufacture calls for but it's getting tougher to get the straight vis stuff. I certainly won't be putting any 0-w30 in my Vair no matter who made the additives until I see some trials on some old engines. You are correct that the oil leaves a film that prevents the metal to metal contact but that film is very, very thin. Look at it this way, with the newer protection packages maybe the thinner oil puts the additives where they're needed more efficiently because it's easier to pump and gets into those small places better. Who knows? I'm not the engineer, I just make the stuff but they try to educate us as well as possible at work because that promotes us taking ownership and making a better product. You sound like an intelligent guy, stick with what makes you comfortable so you won't be worried about it all the time. So long as it's a good brand of oil you have nothing to worry about.

[scottydont]

What you said about the newer oils having better film strength for thin films definitely makes sense. My worry with the old engines was that the gaps between the friction surfaces might be too large and require a thicker film... Anyway, at least for now, I can still find the manufacturer recommended oil. Figure you can't go wrong with that :)

So do corvairs have hardened valve seats? If they do, then the unleaded gas shouldn't be too much of a problem.

[flat6_musik]

I'm guessing that at high rpm, the fan probably takes a good 10-15 hp...

I'd love it if the fan only drew 10-15 HP, I autox my car and regularly spin the engine to 6500 RPM. Here's a fan test by Ray Sedman of American Pi on a late model engine. The two curves are of an engine pull with fan connected, and one with it disabled. At 5500 RPM the difference is 24.3 HP and rising with RPM.

Fan_HP.jpg

It's hard to see the upper blue curve, original picture was a .bmp and for some reason they're not allowed to be posted, so had to convert it to a .jpg with loss of quality. You can see the original picture here:http://www.american-pi.com/corvair/images/Fan_HP.bmp

Marty Scarr

Marty, do you know if Ray actually removed the fan assy and left the belt on, with the alternator spinning, or just removed the belt altogether? I would imagine spinning the alternator, idler pulley and fan bearing would account for a little bit of that.

[martyscarr]

Marty, do you know if Ray actually removed the fan assy and left the belt on, with the alternator spinning, or just removed the belt altogether? I would imagine spinning the alternator, idler pulley and fan bearing would account for a little bit of that.

No, I don't know the details of that dyno test; Scott V, can you shed some light on what went on? But whatever the setup, I don't think the stock alternator would be much of a factor, as even at full load/draw it draws less than 1 HP from the engine, and I doubt the dyno test had every electrical accessory on and the car had a dead battery

Marty Scarr

[flat6_musik]

I don't think the stock alternator would be much of a factor, as even at full load/draw it draws less than 1 HP from the engine, and I doubt the dyno test had every electrical accessory on and the car had a dead battery

Marty Scarr

I seriously doubt that 1 HP number........spinning all the pulleys at higher and higher RPM, I was thinking at least 5 HP. But still, nothing earth-shattering. I just was thinking, if someone wants to truly isolate the exact HP draw of that fan, then they should just remove the fan itself and continue to run the belt with the alternator and pulleys as usual. It just makes for correct testing, IMO.

[miniman82]

What you said about the newer oils having better film strength for thin films definitely makes sense. My worry with the old engines was that the gaps between the friction surfaces might be too large and require a thicker film...

The bearing clearance for these engines isn't any different than other engines, why should they take different oil? The only reason for the additives that the EPA suddenly says harms cat converters was to protect the cam and lifters, the viscosity has nothing to do with that. It's the same argument with the VW guys: thick or thin oil?

If you want my personal opinion, people tend to run oil that is too thick in air cooled engines. Once they switch to a thinner oil and temps go up, they automatically assume something is wrong and go back. Never did they stop to think that maybe the oil was getting around the engine a lot better than the thick stuff was, and make the connection that it's in turn picking up more engine heat because of it. The answer is to shed that heat more effectively and since the Corvair always had a small oil cooler for its displacement, the obvious answer is a larger oil cooler. I've always run 5W-30 in my Corvair, but until the external cooler it was impossible to keep oil temps in check. It's not for everyone though, so most who want to keep a stock look will need to keep on filling their crankcases with 15W-40.

Consequently, if you lose oil pressure or it falls too low with 5W-30 it might be a sign that it's time for a rebuild anyway. Putting in thicker oil always has been a bandaid for sloppy bearings, it will only make the thing quiet temporarily.

So do corvairs have hardened valve seats? If they do, then the unleaded gas shouldn't be too much of a problem.

Yes they do, and unleaded can safely be used.

[scottydont]

Miniman. I've never seen a temperature difference when changing weight of oil. And I monitored oil (and head) temps far more closely than average (right down to accounting for ambient air temp) and played around with different oils and cooling configurations extensively when I was doing the VW thing. The idea that low viscosity oil will somehow pick up more heat from the engine is a stretch at best. No matter the viscosity, an engine oil pump moves a set volume of oil. Viscosity won't change that. I'm guessing that viscosity won't measurably change the thermal absorption properties of the oil either. So unless you think that the oil is somehow leaving the pump and not making it to the bearings and other lubrication surfaces (where it is effectively scattered throughout the entire engine by moving parts no matter what the viscosity is), I fail to see how viscosity will affect cooling with the exception of possibly causing an engine to produce more or less heat from friction, but again, that would likely lead to a failure in short order if there was ever a measurable difference.

Also, I'm willing to bet that if you compare the piston to cylinder wall clearances, ring gaps, lifter bore clearances (where applicable) of 21st century engines to the mid 20th century designs that we're dealing with, you're going to find some notable differences. Even where the gross numbers are the same, the +/- tolerance will likely be much smaller.

If you want to run 5-30 in an engine that was designed and specified to have something else that's fine, and if you don't see any negatives based on the things that are important to you that's just as fine. My personal experience doesn't match yours, but then again neither does my engine, driving style, method of collecting data, or the specific concerns that I have.

Anyway, this is all aside from Herb's topic. No need to clutter things up more than they already are. I'll be happy to discuss it via PM or in a specific thread till the cows come home, but I'm feeling a bit guilty for hijacking the thread here, so I'm bowing out.

[notched]

Thick oil eats horsepower!

[Augie]

I don't work in the Auto Industry any longer(former Process Engineer), but My father, and many of his friends, are, or were power-train engineers. I talk with them, and read a lot, not an expert in engine oil but pretty knowledgeable as far as the engine/oil relationship is concerned. Start here with Bob is the oil guy Oil University. It will give you a good understanding of why we don't use strait weight oils any longer and why you should be using the thinnest oil that is within viscosity spec at operating temps. Which im trying to determine......any help would be appreciated. What im looking for is the Dynamic viscosity range the number will be measured in, Centipoise(CPS), Millipascal seconds(mPas), Poise(P), Saybolt Seconds Universal(SSU), but most likely in Centistokes(cSt), or Stokes(S)


Here is another article that I just dug up that is informative as well. The guy who wrote this is respected on the Bobistheoilguy forums. And he has restored a Corvair or two.
Corvair Oil
Looks like I found the specs....

Chevrolet apparently designed this
engine to run on oil that is between 9.3 cSt and
12.5 cSt in the bearings.

We see here that a typical:

• SAE10W-30 engine oil is in the design viscosity between 92° C and 107° C
• SAE 30 is in the design viscosity between 94° C and 106° C
• SAE 15W-40 is in the design viscosity between 108° C and 121° C
• SAE 20W-50 oil is in the designed viscosity range between 118° C and 130° C.

Note that this means an engine with 20W-50 oil is outside of its ideal range of protection from
the time it is started until the bearings reach 118° C, causing excessive wear.
The first concept to understand when contemplating the difference between single grade (SAE
30) and multigrade (SAE 10W-30) motor oils is that:

• Single grade SAE 30 is just that. It will thicken up in the cold and thin out in the heat
with a fairly steep slope. It is thicker than an xW-30 oil in the cold and thinner at higher
temperatures.

• A multigrade 10W-30 depends on its base oil for its strength.

o A 10W-30 Group I mineral oil is basically a SAE 10 that has polymers that
expand and cause resistance when heated to flow more slowly, acting as a SAE
30 in hot areas of the engine.

o A 10W-30 Group II oil is similar to the Group I oil except that it is much stronger
molecularly and therefore uses fewer polymers.
Selection of the Right Motor Oil for the Corvair and other Engines 12/03/2013 Page 6 of 33

o A 10W-30 synthetic oil is basically a SAE 30 oil that has been created
structurally to act as a SAE 10 when it is
cold. It does not need polymers.

In the Oil University the basic idea that they try to get across( and the correct on IMHO) is to have oil pressure of 10-20 psi at idle and then increasing 10psi for every 1000 RPM. Keeping your operating temp/viscosity relationship within spec. Too thick oil leads to inefficiency in cooling, and too high oil pressure. If your oil is too thin that leads to film breakdown and inefficiency in cooling.

I just purchased a 1962 Monza 4dr with the 2spd powerglide. My guess is after I put pressure and temp gages on the engine oil Ill settle in on a 0w30 or 5w30 synthetic. With the Above Info if I put a thermo to come on at 180 to cool the oil I will be running a 0w30 synthetic. I may add an oil cooler via a oil to water sandwich style fitting that is thermostatically controlled. But first it is getting the $500 basket case running well.

[azdave]

Oil?

When it comes to oil choice and filter choice I put my faith in Richard1's opinions. He's a dedicated Corvair owner and driver as well so he knows our needs. He's also not out to sell me anything.

Richard is well respected on both this forum and corvaircenter as the "go to guy" to sort out all of the claims made by different oil and filter companies.
He has links in his signature to all of his papers and documents.

Here is a post he made about oils of yesteryear. See his signature for related links.
viewtopic.php?f=55&t=5387&p=36469&hilit ... air#p36469

Keep in mind that until I personally have an oil related failure on one of my engines I don't stress out too much about what oil and filter I use. I follow Richard's basic guidelines then go out and drive. I don't loose sleep at night because I'm running 10W40 or 10W30.

[Augie]

Keep in mind that until I personally have an oil related failure on one of my engines I don't stress out too much about what oil and filter I use. I follow Richard's basic guidelines then go out and drive. I don't loose sleep at night because I'm running 10W40 or 10W30.

If you paid attention to the articles I posted they are written by Richard Widman...

The way I read his stuff is that you should be on a (xx)w30 weight unless there are issues with your engine(it is failing) or you know the operating temp is higher than 106C.


If I have interpreted Richard's paper wrong I apologize..... but I dont think I have....

[azdave]

Keep in mind that until I personally have an oil related failure on one of my engines I don't stress out too much about what oil and filter I use. I follow Richard's basic guidelines then go out and drive. I don't loose sleep at night because I'm running 10W40 or 10W30.

If you paid attention to the articles I posted they are written by Richard Widman...

The way I read his stuff is that you should be on a (xx)w30 weight unless there are issues with your engine(it is failing) or you know the operating temp is higher than 106C.


If I have interpreted Richard's paper wrong I apologize..... but I dont think I have....

Sorry. I was just skimming the topic and saw "Bob is the Oil Guy" mentioned but not that you already read Richard1's info.

I've had many high mileage Fords and Chevys (150-200K miles) that have almost always received a cheap Fram filter and whatever was on sale at Autozone. The engines still ran fine with good oil pressure when the other major components gave out and ended their economic usefulness so I figure the cheap oil and filters have served me just fine.

YMMV

[Augie]

Sorry. I was just skimming the topic and saw "Bob is the Oil Guy" mentioned but not that you already read Richard1's info.

I've had many high mileage Fords and Chevys (150-200K miles) that have almost always received a cheap Fram filter and whatever was on sale at Autozone. The engines still ran fine with good oil pressure when the other major components gave out and ended their economic usefulness so I figure the cheap oil and filters have served me just fine.

YMMV

Ahhhh So if you run across the freeway 10 times and do not get hit, is running across the freeway a good idea?

Most of the time you are right, their isn't really a "bad" oil made today, but with a little research you can run a better oil and remove one variable that results in failure...

[Corvair1]

Added a little more and will be starting her up this Thursday.

[azdave]

Looking really good Herb!

[BIGTWIN]

That's a great looking engine Herb. Good luck with the cooling experiments.